Inclined Fire, part #3.5bis: 2I2R for victims of MOA
And now folks, a special edition of the 2I2R for unfortunate owners of scopes with clicks graduated in ¼MOA. (Many of my good friends fell victims of this perversion; US manufacturers of [otherwise excellent] scopes seem to love this.)
Improved Rifleman's rule:
1. Measure the inclination α;
2. Measure the slant distance (along LOS) D;
3. Look up bullet path (come-up) in ballistic table as if shooting at distance D horizontally;
4. Multiply this correction by cos(α).
The secret ingredient, 2I2R-MOA:
5. Subtract one click per each five degrees of inclination over twenty, i.e., 25º -1 click, 30º -2 clicks, 35º -3 clicks, etc.
Results for three different calibres, for the price of one -- check it out:
GP11 2I2R-MOA vertical miss distance, cm
| 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | |
| 300 | 1.1 | 2.0 | 0.9 | 0.0 | -0.8 | -1.4 | -1.9 | -2.0 | -2.0 | -1.7 |
| 400 | 1.4 | 2.7 | 1.3 | 0.0 | -1.0 | -1.6 | -2.0 | -2.2 | -2.0 | -1.3 |
| 500 | 1.6 | 3.1 | 1.3 | -0.2 | -1.4 | -2.2 | -2.7 | -2.7 | -2.3 | -1.2 |
| 600 | 1.7 | 3.5 | 1.1 | -0.6 | -2.2 | -3.2 | -3.7 | -3.6 | -3.0 | -1.5 |
| 700 | 1.5 | 3.6 | 0.8 | -1.6 | -3.3 | -4.5 | -5.1 | -5.2 | -4.3 | -2.4 |
| 800 | 1.2 | 3.2 | -0.1 | -2.9 | -5.0 | -6.5 | -7.3 | -7.3 | -6.4 | -4.2 |
| 900 | 0.5 | 2.5 | -1.5 | -4.8 | -7.4 | -9.3 | -10.4 | -10.5 | -9.5 | -6.9 |
| 1000 | -0.7 | 1.2 | -3.7 | -7.7 | -10.9 | -13.4 | -14.8 | -15.3 | -14.2 | -11.5 |
| -15 | -20 | -25 | -30 | -35 | -40 | -45 | -50 | -55 | -60 | |
| 300 | 1.2 | 2.2 | 1.2 | 0.2 | -0.5 | -1.1 | -1.5 | -1.7 | -1.6 | -1.5 |
| 400 | 1.9 | 3.3 | 1.9 | 0.7 | -0.1 | -0.7 | -1.0 | -1.1 | -0.9 | -0.1 |
| 500 | 2.5 | 4.3 | 2.7 | 1.4 | 0.4 | -0.1 | -0.5 | -0.5 | 0.2 | 1.2 |
| 600 | 3.2 | 5.6 | 3.8 | 2.4 | 1.2 | 0.6 | 0.4 | 0.6 | 1.5 | 3.1 |
| 700 | 4.2 | 7.1 | 5.1 | 3.6 | 2.5 | 1.9 | 1.8 | 2.3 | 3.4 | 5.6 |
| 800 | 5.5 | 8.9 | 6.9 | 5.4 | 4.3 | 3.9 | 3.9 | 4.7 | 6.2 | 8.6 |
| 900 | 7.1 | 11.2 | 9.2 | 7.7 | 6.8 | 6.5 | 6.8 | 7.9 | 9.6 | 12.7 |
| 1000 | 9.0 | 14.0 | 12.1 | 10.9 | 10.2 | 10.1 | 10.8 | 12.1 | 14.5 | 18.1 |
GP90 2I2R-MOA vertical miss distance, cm
| 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | |
| 300 | 1.1 | 2.1 | 1.0 | 0.1 | -0.7 | -1.3 | -1.6 | -1.8 | -1.8 | -1.6 |
| 400 | 1.6 | 2.9 | 1.6 | 0.4 | -0.4 | -1.0 | -1.3 | -1.3 | -0.8 | 0.2 |
| 500 | 2.0 | 3.7 | 2.0 | 0.7 | -0.3 | -0.9 | -1.0 | -0.7 | 0.1 | 1.9 |
| 600 | 2.3 | 4.4 | 2.5 | 0.9 | -0.1 | -0.7 | -0.8 | -0.3 | 1.2 | 3.5 |
| 700 | 2.9 | 5.3 | 3.1 | 1.3 | 0.1 | -0.4 | -0.3 | 0.5 | 2.4 | 5.5 |
| 800 | 3.3 | 6.1 | 3.6 | 1.7 | 0.4 | -0.1 | 0.0 | 1.2 | 3.5 | 7.5 |
| 900 | 3.2 | 6.1 | 3.1 | 0.8 | -0.7 | -1.4 | -1.1 | 0.1 | 2.8 | 7.4 |
| 1000 | 1.3 | 4.0 | 0.0 | -3.1 | -5.3 | -6.6 | -6.7 | -5.7 | -2.9 | 2.2 |
| -15 | -20 | -25 | -30 | -35 | -40 | -45 | -50 | -55 | -60 | |
| 300 | 1.3 | 2.2 | 1.2 | 0.2 | -0.6 | -1.2 | -1.6 | -1.8 | -1.8 | -1.6 |
| 400 | 1.7 | 3.1 | 1.8 | 0.7 | -0.2 | -0.7 | -1.0 | -1.0 | -0.5 | 0.4 |
| 500 | 2.2 | 4.0 | 2.4 | 1.2 | 0.2 | -0.3 | -0.4 | -0.2 | 0.7 | 2.3 |
| 600 | 2.8 | 4.9 | 3.1 | 1.6 | 0.6 | 0.1 | 0.0 | 0.6 | 1.9 | 4.1 |
| 700 | 3.3 | 5.9 | 3.8 | 2.1 | 1.0 | 0.4 | 0.4 | 1.1 | 2.9 | 5.7 |
| 800 | 3.7 | 6.7 | 4.2 | 2.4 | 1.1 | 0.6 | 0.7 | 1.6 | 3.7 | 7.1 |
| 900 | 4.9 | 8.5 | 6.0 | 4.2 | 3.0 | 2.6 | 3.0 | 4.3 | 6.8 | 11.0 |
| 1000 | 7.7 | 12.3 | 10.2 | 8.8 | 8.2 | 8.4 | 9.4 | 11.3 | 14.7 | 19.8 |
.338LM 2I2R-MOA vertical miss distance, cm
| 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 | |
| 300 | 0.9 | 1.7 | 0.3 | -0.9 | -2.2 | -3.3 | -4.4 | -5.6 | -6.8 | -8.4 |
| 400 | 1.2 | 2.2 | 0.5 | -1.2 | -2.7 | -4.1 | -5.5 | -6.9 | -8.3 | -9.8 |
| 500 | 1.5 | 2.8 | 0.6 | -1.5 | -3.3 | -5.0 | -6.6 | -8.2 | -9.8 | -11.5 |
| 600 | 1.7 | 3.2 | 0.7 | -1.8 | -4.0 | -6.0 | -7.9 | -9.7 | -11.5 | -13.4 |
| 700 | 1.8 | 3.6 | 0.5 | -2.3 | -5.0 | -7.2 | -9.4 | -11.5 | -13.5 | -15.5 |
| 800 | 2.0 | 4.0 | 0.4 | -2.9 | -5.9 | -8.6 | -11.0 | -13.3 | -15.3 | -17.6 |
| 900 | 2.1 | 4.2 | 0.2 | -3.6 | -6.9 | -9.9 | -12.7 | -15.3 | -17.6 | -19.9 |
| 1000 | 2.0 | 4.4 | -0.2 | -4.4 | -8.1 | -11.6 | -14.5 | -17.4 | -20.0 | -22.4 |
| -15 | -20 | -25 | -30 | -35 | -40 | -45 | -50 | -55 | -60 | |
| 300 | 1.0 | 1.8 | 0.4 | -0.8 | -2.0 | -3.2 | -4.3 | -5.4 | -6.7 | -8.2 |
| 400 | 1.4 | 2.5 | 0.7 | -0.8 | -2.4 | -3.7 | -5.1 | -6.5 | -7.8 | -9.4 |
| 500 | 1.8 | 3.3 | 1.1 | -0.8 | -2.5 | -4.1 | -5.8 | -7.2 | -8.9 | -10.7 |
| 600 | 2.3 | 4.2 | 1.6 | -0.5 | -2.6 | -4.4 | -6.2 | -8.0 | -9.7 | -11.6 |
| 700 | 2.8 | 5.0 | 2.2 | -0.4 | -2.6 | -4.7 | -6.7 | -8.7 | -10.6 | -12.5 |
| 800 | 3.5 | 6.0 | 2.8 | 0.0 | -2.4 | -4.8 | -6.9 | -9.1 | -11.1 | -13.2 |
| 900 | 4.3 | 7.1 | 3.7 | 0.6 | -2.3 | -4.8 | -7.1 | -9.4 | -11.5 | -13.9 |
| 1000 | 4.9 | 8.2 | 4.3 | 1.1 | -2.0 | -4.8 | -7.2 | -9.6 | -12.0 | -14.4 |
Is it not terrific?